The study, by Maria Prendecki, MBBS, of the Imperial College Renal and Transplant Centre, Hammersmith Hospital, London, and colleagues, included 187 patients with biopsy-proven AIN, of whom 158 were treated with steroids and 29 were managed conservatively. All steroid-treated patients received oral prednisolone, with most patients prescribed either 40 or 60 mg of prednisolone daily. Three of these patients also received intravenous methylprednisolone. Of the 187 patients, 48 had clearly defined drug-induced AIN and 26 patients had tuberculosis-associated AIN.

At presentation, the patients had a median age of 52.4 years. The median follow-up was 39 months. The steroid-treated patients did not differ from those not treated with steroids with respect to median eGFR or dependence on renal replacement therapy (RRT) at the time of biopsy.

The steroid group had significantly higher eGFR at all time points post-biopsy up to 24 months, when the median eGFR was 43 mL/min/1.73 m2 in the steroid recipients compared with 24 mL/min/1.73 m2 in the untreated patients, a statistically significant difference between the groups, the investigators reported online ahead of print in the Clinical Kidney Journal. A significantly smaller proportion of steroid-treated patients compared with the untreated patients were RRT dependent by 6 months (3.2% vs. 20.6%) and 24 months (5.1% vs 24.1%.

Dr Predecki’s team noted that the role of steroids in AIN treatment remains controversial, with no prospective randomized controlled trials testing this therapy and conflicting findings from retrospective series. Based on their results, the investigators wrote, they would suggest the use of oral prednisolone at a dose of 1 mg/kg, with a maximum dose of 60 mg daily. “Ideally, steroids should be rapidly weaned over the next 8–12 weeks to avoid the recognized complications.”

In their acknowledgement of study limitation, the investigators pointed out their study involved a retrospective series with some missing data and multiple clinicians at their center treated AIN patients with no defined protocol for steroid use due to the lack of evidence. In addition, the decision to treat with steroids or not was at the discretion of the clinician. “We therefore report a heterogenous group of patients with considerable variation in steroid dose and duration,” they wrote. “There was also variation in time to introduction of steroids, from within hours of biopsy to a few weeks.”

Dr Predecki and her collaborators also pointed out that more patients were treated with steroids than were not, “which makes statistical analysis of subgroups difficult due to small numbers in the non-steroid-treated group.”